Time Zones Around the World Explained
Quick Answer: UTC Offsets for Major Cities
| City | Offset (Winter) | Offset (Summer) |
|---|---|---|
| London (GMT/BST) | UTC+0 | UTC+1 |
| New York (EST/EDT) | UTC-5 | UTC-4 |
| Los Angeles (PST/PDT) | UTC-8 | UTC-7 |
| Dubai (GST) | UTC+4 | UTC+4 (no daylight saving) |
| Mumbai and Delhi (IST) | UTC+5:30 | UTC+5:30 (no daylight saving) |
| Karachi and Lahore (PKT) | UTC+5 | UTC+5 (no daylight saving) |
| Sydney (AEST/AEDT) | UTC+10 | UTC+11 |
| Tokyo (JST) | UTC+9 | UTC+9 (no daylight saving) |
| Singapore (SGT) | UTC+8 | UTC+8 (no daylight saving) |
Understanding time zones is essential for international business, remote work, travel planning and coordinating calls across countries. This guide explains how time zones work, gives you current offsets for every major region and shows you how to use the free Time Converter on CalConvs for duration and time unit conversions.
How Time Zones Work
The earth is divided into 24 standard time zones, each roughly 15 degrees of longitude wide, corresponding to one hour of rotation. The reference point is Coordinated Universal Time (UTC), formerly known as Greenwich Mean Time (GMT). All time zones are expressed as offsets from UTC.
UTC+5:30 means a location is 5 hours and 30 minutes ahead of UTC. UTC-8 means a location is 8 hours behind UTC. India uses a half-hour offset (UTC+5:30) while some countries like Nepal and Iran use 45-minute offsets, making them unusual among global time zones.
Time Zone Reference: Major Cities and Regions
| UTC Offset | Major Cities | Notes |
|---|---|---|
| UTC-8 / -7 | Los Angeles, San Francisco, Vancouver | PST in winter, PDT in summer |
| UTC-7 / -6 | Denver, Phoenix, Calgary | MST in winter, MDT in summer |
| UTC-6 / -5 | Chicago, Mexico City | CST in winter, CDT in summer |
| UTC-5 / -4 | New York, Toronto, Miami | EST in winter, EDT in summer |
| UTC-3 | Buenos Aires, Sao Paulo | No daylight saving in Argentina |
| UTC 0 / +1 | London, Dublin, Lisbon | GMT in winter, BST in summer |
| UTC+1 / +2 | Paris, Berlin, Rome, Madrid | CET in winter, CEST in summer |
| UTC+2 / +3 | Cairo, Istanbul, Nairobi | Varies by country |
| UTC+3 | Moscow, Riyadh, Baghdad | No daylight saving in most Gulf states |
| UTC+4 | Dubai, Abu Dhabi, Baku | GST all year, no daylight saving |
| UTC+5 | Karachi, Lahore, Islamabad, Tashkent | PKT all year |
| UTC+5:30 | Mumbai, Delhi, Kolkata, Colombo | IST all year |
| UTC+5:45 | Kathmandu | NPT, unusual 45-minute offset |
| UTC+6 | Dhaka, Almaty | BST all year |
| UTC+7 | Bangkok, Jakarta, Ho Chi Minh City | ICT all year |
| UTC+8 | Singapore, Kuala Lumpur, Beijing, Hong Kong, Perth | SGT/CST/AWST all year |
| UTC+9 | Tokyo, Seoul | JST/KST all year |
| UTC+10 / +11 | Sydney, Melbourne, Brisbane | AEST in winter, AEDT in summer |
| UTC+12 | Auckland, Fiji | NZST in winter, NZDT in summer |
Daylight Saving Time: Which Countries Use It?
Daylight Saving Time (DST) is the practice of advancing clocks by one hour in spring and reverting in autumn, extending daylight into evening hours. Not all countries observe it.
- United States and Canada: Yes. Clocks spring forward in March and fall back in November. Arizona (US) does not observe DST.
- United Kingdom and Europe: Yes. UK clocks change in March and October. European countries change on the same dates.
- Australia: Yes in most states. New South Wales, Victoria, South Australia and ACT observe DST. Queensland, Western Australia and Northern Territory do not.
- India: No. IST (UTC+5:30) is constant all year.
- Pakistan: No. PKT (UTC+5) is constant all year.
- UAE, Saudi Arabia, Qatar: No. Gulf states do not observe DST.
- Japan, China, Singapore: No. None of these countries observe DST.
How to Calculate Time Differences
To find the time difference between two cities, subtract one UTC offset from the other.
- London to New York: 0 - (-5) = 5 hours. London is 5 hours ahead of New York.
- Dubai to London: 4 - 0 = 4 hours. Dubai is 4 hours ahead of London.
- Lahore to New York: 5 - (-5) = 10 hours. Lahore is 10 hours ahead of New York.
- Sydney to Los Angeles: 10 - (-8) = 18 hours. Sydney is 18 hours ahead of Los Angeles.
Best Times to Schedule International Calls
| Route | Best Overlap Window |
|---|---|
| London to New York | 2pm to 5pm London (9am to 12pm New York) |
| London to Dubai | Good overlap throughout the working day |
| London to Mumbai | 9am to 1pm London overlaps with Mumbai office hours |
| New York to Lahore | Very limited practical overlap |
| Singapore to Dubai | 9am to 2pm Singapore (early morning Dubai) |
Frequently Asked Questions
What is the time difference between India and the UK?
India (IST, UTC+5:30) is 5 hours and 30 minutes ahead of the UK when the UK is on GMT (winter). During British Summer Time (BST, UTC+1), India is 4 hours and 30 minutes ahead.
What is the time difference between Pakistan and the UK?
Pakistan (PKT, UTC+5) is 5 hours ahead of the UK in winter (GMT). During British Summer Time (UTC+1), Pakistan is 4 hours ahead.
What is the time difference between Dubai and the US?
Dubai (UTC+4) is 9 hours ahead of New York (UTC-5) in winter. It is 12 hours ahead of Los Angeles (UTC-8) in winter. During US daylight saving, these gaps reduce by one hour.
Does India have daylight saving time?
No. India does not observe daylight saving time. Indian Standard Time (IST) is UTC+5:30 throughout the entire year. The same applies to Pakistan (PKT, UTC+5), which also does not observe daylight saving.
What country is UTC+5:30?
India and Sri Lanka both use UTC+5:30. India calls this Indian Standard Time (IST). Nepal uses UTC+5:45. Pakistan uses UTC+5 (PKT), which is 30 minutes behind IST.
Related Tools
- Time Converter: convert between seconds, minutes, hours, days and weeks
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